Device for determining diameters.



J. G. AYERS, JR. DEVICE FOR DETERMINING DIAMETERS.

APPLIOATION FILED DEC. a, 1909.

979,24& Patanted; Dec. 20, 1910.

ATTORNEYS circle is complete,

JOSEPH enamsn arnnsfra, or STEELTON,

PENNSYLVANIA.

DEVICE FOB DETERMINING DIAMETERS.

, 'Speciflcation of Letters Patent. Application filed December 3, 1909.Serial No.

Patented Dec. 20, 1910. 531,238.

To all whom it may concern: y 7 Be it known that I, J osnrn G. Areas, Jr., a citizen of the United States, and a resident of Steelton, in thecounty of Dauphin and State of Pennsylvania, have invented a new andImproved Device for Determining Diameters, of which the following is afull, clear, and exact description.

This invention'relates to certain improvements in measuring devices, andthe object of the invention is to provide whereby the diameter of a orthe radius of readily ascertained.

It is a comparatively easy matter to as certain the diameter of a circlewhen the and various different forms of devices may be employed foraccomplishing the 1purpose, but my improved device is especia lydesigned for ascertaining the radius or diameter of a curve when only anarc of the curve is present or intact.

he invention is particularly useful for determining the diameter of anengine cylinder when onlya portion of the whole of the cylinder isavailable, or for determining the diameter of a sewer ipe or conduit, orof a gournal box from a fi-agment or section whic presents only aportion of the complete cylindrical surface.

y improved device is extremely simple in construction, and embodies onlytwo essential elements with means for holding them in" fixedrelationship. One of these elements or members is designed to have itsends engage with different portions of the cylindricalsurface, so thatthe member extends alon a chord of, the cylinder and the other mem er iscarried by the first member and is movable in respectthereto, to engagewith a third point on the surface. The relative ositions of'the. twomembers, whensaid mem ers are in proper position,are directly dependentupon the diameter of the cylinder or bore, and, in fact determine thedi. ameter. Y I

Theinvention may assume various diiferent orms as far as the details ofconstruction. are concerned, but a simple and efficient form is thatillustrated in the drawingsand after.

Reference .is to be had to ing fication, in w a device described more-indetail hereinforming a part of this specithe I axis, irrespective theaocompany- 'ch similar characters of reference indicate correspondingparts in both the figures, and in which Figure 1 is a perspective viewof a device constructed in accordance with my invention, and inoperative position in respect to a body presenting a portion of acylindrical surface; and Fig. 2 is a diagram showing the relationship ofthe parts within the por tion of the cylinder, the complete circle beingshown in dotted outline.

In its preferred form, my improved device includes a bar or plate 10,preferably of steel and of sufiicient thickness to normally remain rigidwith its edges straight and true. The form of the side edges of the baror plate is immaterial, but the ends of the bar or plate presentstraight edges 11, parallel to each other and at right angles to thegeneral direction of the bar. The bar may be made in various lengthsdependent upon the character of the work to be measured, and is of suchlength that it may be inserted within the cylinder and may lie along achord of the circle. The two end edges 11 are ada ted to engage directlywith the curved surface, and constitute elements of said surface. Theedges 11 ma be of any length desired, but they are preterably of suchlength that they will insure holding of the bar 10 with its uppersurface in a plane arallel to the axis of the circle, and with t e edges11 parallel to the of any slight defects or irregularities in theportion of the surface with which said edges-engage. The bar 10 carriesa second bar 12, mounted exactly half-way between the ends of the bar10, and disposed at right angles to said bar. For guiding the bar 12 andholding it against twisting or turning movement, the bar 10 preferablycarries a guiding sleeve 13," which is rigidly secured to said bar 10and has an aperture lengthwise thereof,

' through which the bar 12 may slide. The

sleeve at one side screw 14, by means be locked m 10. The bar 12 may beof any desired form in cross section, but it is preferablynoncylindrical in cross section, so that it cannot rotate within thetube or sleeve 13, and the lower edge of the bar 12 preferablyterminates in a sharpedge 15, extending parallel to the two edies 15 isof suflieient lengt so that it wil not thereof, may carry a set of whichthe bar 12 may position in respect to the bar edge rests on the curvedenter into any very slight irregularities or The minimum readingcavities in the surface.

In using my improved device, is placed with its opposite ends inengagement with the curved-surface to be measured, andthe bar is soplaced that it will extend across a portion of the curve and constitutea chord thereof. The forming of the ends with arallel edges 11, insuresthe median line of the bar 10 occupying a position in a plane at rightangles to the axis of the bore or cylinder. The bar 12 is then permittedto drop until its lower surface. The three edges 11, 11 and 15 thusengage with three elements of the cylindrical surface. As three pointsdetermine a circle, so each three elements determine a cylindricalsurface, and therefore there can be but one true cylinder for eachadjustment. of the bar 12 in respect to the bar 10. The bar 12 ispreferably calibrated, to give directly the diameter of the cylindersurface when the bars or members 10 and 12 are in proper position.

The calibration on the bar 12 may be obtained by the use of the formulaConsidering the diagram shown in Fig. 2, the bar 10 may be representedby the line A B, and the bar 12 by the line C E. The diameter of thecircle would be E F. The line A C, which represents one-half the lengthof the bar 10, is at right anglesto the line E F, which represents thediameter of the circle. The line A C is the mean proportional betweenthe sections E C and C F of the diameter, and therefore the diameter E Fis equal to 1 2 A C +.E 0.

To simplify the formula, the line E F or diameter may be called D;-theline E C, which represents the height of the chord, may be called theletter H, and the line A C, which represents one-half the chord, theletter P. Thus D Hi.

the bar 10 portion of the The bar 10 would then lie will be at the upperedge of the collar 13 when the length of the bar 12 below the bar 10 isequal to one-half the length of the bar 10. along a diameter of thecircle. The greater the diameter of the circle, the shorter will be theportion of the bar 12 below the bar 10.

My improved device is especially designed for ascertaining the diameterwhen only a portion of the circumference is present, or in suchcondition that it may be measured from, but it is of course evident thatthe device may be used equally well when the whole cylindrical surfaceis intact. Upon placing the device in engagement with the cylindricalsurface, it automatically assumes the proper position in respectthereto. The edges 11 insure the proper positioning of the bar 10, andthe bar 12 will slide down until it engages with the surface. It ismerely necessary to place the device in position, be sure that it restssteady, and then tighten the screw 1i, after which the device may beremoved and the reading taken.

Instead of marking the subdivisions on the'bar 12 to indicate thedifferent diameters or radii, I may, if desired, and in fact, Ipreferably divide the bar 12 into hundredths of an inch, and provide onthe bar 10, a table or list showing the different radii or differentdiameters corresponding to each graduation on'the bar 12. This permitsthe graduations or subdivisions on the bar 12 to be of uniform distanceapart, and simplifies the marking. Furthermore, it permits the bar 12 tobe removed and used for direct measuring of short distances.

Having thus described my invention, I claim as new and desire to secure.by Letters Patent:

A device for determinin prising a bar adapted to he within a chord of. ac linder and having straight edges at its en s for engagingwith elementsof the diameters, comcylindrical surface, and a second bar carried bythe first-mentioned bar at right angles thereto and intermediate itsends, sai second-mentioned "bar being. longitudinally movable and havingone end presenting a straight edge for engagement with the cylindricalsurface along a third element thereof, and being calibrated to indicatethe diameter of the cylinder when the three edges are in engagement withthe cylindrical surface, and means for locking said bars againstrelative movement. In-testimony whereof I have signed my name to thisspecification in the presence of two subscribing witnesses.

JOSEPH GERRISH AYERS, JR.

Witnesses:

WALTON Bou'mnnn FULLER, PAUL THOMAS Lasimn.

